Castello della Valle (Fiumefreddo Castle), founded in 1201, was the residence of the noble lords. During the mid-16th-century, the castle was donated to Ferdinando De Alarçon-Mendoza, marquis of the Valle, and took its current name of Castello della Valle. The current appearance dates from that age. The castle was besieged in 1806-1807 by French troops and nearly destroyed. Today it houses several works of local painter Salvatore Fiume.
Towering 52 meters above the sea, Bengtskär lighthouse is the tallest one in Scandinavia. The building started in in 1905 after the shipwreck of S/S Helsingfors and was completed in 1906. The lighthouse was designed by architect Florentin Granholm. On December a special petrol lantern, designed and built in Paris, was brought to Bengtskär and installed atop the tower.
German fleet bombarded Bengstkär in the First World War in 1914. Since the Gulf of Finland was heavily mined, it was not until 1919 that the surrounding seas were declared safe for shipping, that the light was lit again.
After the war the military value of Bengtskär increased as part of the defence system of independent Finland. In Second World War (1941) Soviet Union made a suprise attack to island. After a bloody battle, the small Finnish garrison emerged victorious. Intermittent repairs to the facility continued during the post-war period.